Eco-friendly membranes for separations

Abstract

A method of fabricating an eco-friendly, porous membrane includes preparing a porous membrane using a dope solution of polymer, dimethyl sulfoxide (DMSO), and one or more deep eutectic solvents (DES). The porous PLA membrane can be formed from the dope solution through non-solvent induced phase separation (NIPS). A concentration of the one or more deep eutectic solvents in the dope solution can be between about 0.5 and 3.0 weight percent. The one or more deep eutectic solvents results in the membrane having increased porosity and a larger average pore size diameter. In an example, the one or more deep eutectic solvents includes choline chloride (ChCl) and ethylene glycol (EG). In an example, the membrane can be used for oil-water separation and the oil rejection of the membrane is at least 80 percent.

1 . A method of forming a porous membrane, the method comprising: preparing a porous membrane using a dope solution of polymer, dimethyl sulfoxide (DMSO), and one or more deep eutectic solvents (DES). 
     
     
         2 . The method of  claim 1 , further comprising casting the dope solution to form a film; and immersing the film in a coagulation bath to form the porous membrane. 
     
     
         3 . The method of  claim 1 , wherein the polymer is polylactic acid (PLA). 
     
     
         4 . The method of  claim 1 , wherein the dope solution is formed by:
 forming or providing a first solution of the one or more deep eutectic solvents;   mixing a DMSO solvent and the polymer to dissolve the polymer and form a second solution; and   mixing the first solution and second solution together to form the dope solution.   
     
     
         5 . The method of  claim 1 , wherein the one or more deep eutectic solvents includes a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD). 
     
     
         6 . The method of  claim 5 , wherein a molar ratio of HBA to HBD in the dope solution is about 1:2. 
     
     
         7 . The method of  claim 5 , wherein the HBA is choline chloride (ChCl). 
     
     
         8 . The method of  claim 5 , wherein the HBD is ethylene glycol (EG). 
     
     
         9 . The method of  claim 1 , wherein an amount of the one or more deep eutectic solvents (DES) in the dope solution is between about 0.5 wt. % and 3.0 wt. %. 
     
     
         10 . The method of  claim 1 , wherein an average pore size diameter of the porous membrane is between about 70 and 100 nm. 
     
     
         11 . The method of  claim 1 , wherein a porosity of the porous membrane is between about 70 and 90 percent. 
     
     
         12 . An ultrafiltration membrane formed by the method of  claim 1 . 
     
     
         13 . A method of fabricating an ultrafiltration membrane, the method comprising: forming a deep eutectic solvent (DES) solution of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD); forming a polymer solution by dissolving a PLA polymer in dimethyl sulfoxide (DMSO); mixing the DES solution and the polymer solution to form a dope solution; casting the dope solution onto a plate; and immersing the plate in a coagulation bath to form a porous PLA membrane; and optionally rinsing the porous PLA membrane to remove residual solvents and impurities. 
     
     
         14 . The method of  claim 13 , wherein the HBA is choline chloride (ChCl) and the HBD is ethylene glycol (EG). 
     
     
         15 . The method of  claim 14 , wherein a molar ratio of ChCl to EG is about 1:2. 
     
     
         16 . The method of  claim 13 , wherein a sum of the HBA and the HBD in the dope solution is between about 0.5 wt. % and 3.0 wt. %. 
     
     
         17 . A method of separating oil and water using an ultrafiltration membrane, the method comprising:
 fabricating an ultrafiltration membrane from PLA, dimethyl sulfoxide (DMSO) and one or more deep eutectic solvents (DES) using non-solvent induced phase separation; and   filtering an oil-water emulsion through the ultrafiltration membrane to remove oil from water.   
     
     
         18 . The method of  claim 17 , wherein oil rejection is at least 90%. 
     
     
         19 . The method of  claim 17 , wherein an amount of oil in the oil-water emulsion ranges from about 100 ppm to about 1000 ppm. 
     
     
         20 . The method of  claim 17 , wherein a permeate flux of the ultrafiltration membrane is at least 800 LMH.